Process of removing polyvinyl alcohol size from fabrics with hydrogen peroxide

ABSTRACT

A PROCESS FOR REMOVING POLYVINYL ALCOHOL SIZE FROM FABRICS WITH HYDROGEN PROVIDED COMPRISES CONTACTING THE FABRIC WITH AN AQUEOUS SOLUTION OF DILUTE HYDROGEN PEROXIDE IN THE PRESENCE OF IRONS OF CERTAIN TRANSITION METALS.

United States Patent ABSTRACT OF THE DISCLOSURE A process for removing polyvinyl alcohol size from fabrics with hydrogen peroxide comprises contacting the fabric with an aqueous solution of dilute hydrogen peroxide in the presence of ions of certain transition metals.

I This is a continuation-in-part of application Ser. No. 141,406, filed May 7, 1971, now abandoned.

BACKGROUND OF THE INVENTION Field of the Invention This invention relates to the removal of polyvinyl alcohol size from fabrics. More particularly, it relates to a method employing certain transition metal catalysts to improve removal of polyvinyl alcohol size with aqueous hydrogen peroxide.

The Prior Art In the manufacture of textiles, it is common to treat warp yarns with a size coating prior to weaving into a fabric. Typically, starch is used as sizing agent. While an effective size for cellulosic fibers, such as cotton and the like, starch has relatively poor adhesion to many synthetic fibers. Polyvinyl alcohol has become increasingly important as a replacement for starch in warp sizing. Polyvinyl alcohol exhibits excellent adhesion to synthetic fibers (particularly polyesters) and also provides a greater sizing effect per weight of size, one pound of polyvinyl alcohol being equivalent to about three to five pounds of starch, thus permitting faster processing and less thread breakage.

Following weaving of the sized fibers, the sizing agent must be removed prior to further fabric finishing opera.- tions such as bleaching, dyeing, and the like. Amylase systems are generally used to desize starch-sized fabrics but are ineffective with polyvinyl alcohol. Polyvinyl alcohol is conventionally desized with hot water-detergent combina tions or hot-'water-mineral spirits emulsions, These conventional desizing procedures require steaming and wash ing temperatures of about 190'2l2 F. to be effective. Even at these high temperatures, conventional desizing procedures often leave relatively high levels of polyvinyl alcohol in the fabric. This residual polyvinyl alcohol may loosen in subsequent finishing operations, such as alkaline scouring or dyeing, and in these alkaline media, gell, and redeposit as spots on the fabric surface or seriously clog finishing equipment.

Hydrogen peroxide solutions have been proposed as an alternative to the conventional desizing solutions. Du Pont Sales Bulletin, Removal of Elvanol from Fabric, pages 7 and 8, suggests desizing with conventional hydrogen peroxide bleaching solutions, that is, solutions containing caustic and sodium silicate in addition to hydrogen peroxide and having pl-ls of 9 or greater. These solutions have not proven effective since they leave substantial residual size and pose color and odor problems.

In my patent with Gerald R. Ferrante, US. 3,682,583, it is disclosed that hydrogen peroxide solutions having lower pI-I's (pH 4-9) are far more effective for polyvinyl alcohol desizing than bleach solutions. While this low pH process does give good results it and the alkaline bleach desizing process as well for best results require relatively high temperatures (180 F.) or greater. These temperatures are difficult to achieve in many commercial facilities without special equipment. Lower temperatures generally require longer contact times.

STATEMENT OF THE INVENTION It has now been found that the polyvinyl alcohol desizing ability of aqueous hydrogen peroxide solutions can be materially improved by using therewith transition metal ions which catalyze peroxide decomposition. In a preferred embodiment in the presence of catalytic amounts of metal ions of iron, cobalt or copper, polyvinyl alcohol size is desized using solutions of hydrogen peroxide rapidly at temperatures as low as about F.

DETAILED DESCRIPTION OF THE INVENTION The Desizing Solution The improved desizing solution is an aqueous solution of hydrogen peroxide which additionally contains ions of certain transition metals and optionally a surface active Preferred metal ions are the ions of iron, cobalt, and cop'- per; with cobalt and copper ions preferred. Copper is particularly preferred as effective at extremely low concentrations.

The amount of metal ion present in the instant desizing solutions is generally selected in the range of about 0.1 to about 10,000 p.p.m. When the metal is iron or cobalt concentrations of from about 20 p.p.m. to about 10,000 p.p.m. by weight, preferably of from p.p.m. to about 5,000 p.p.m. being employed with ion concentrations of from 100 to 1,000 p.p.m. by weight being most preferred. Copper is very effective at concentrations as low as about 0.5 p.p.m. based upon the aqueous peroxide solution. However, it is preferred to employ concentrations of from about 1.0 to about 100 p.p.m., especially from about 2 to about 20 p.p.m. Larger amounts may be used if desired, but are not generally required. The source of metal ions is not critical. The metal ions can be added as water soluble salts of organic or mineral acids or as soluble complexes. For example, iron can be added as ferric chloride,

ferric ammonium oxalate, ferric sulfate, ferrous nitrate and the like; cobalt can be added as cobalt acetate, cobalt chloride, cobalt sulfate, added as copper sulfate, copper nitrate, copper chloride, copper lactate and the like.

Preferred sources of metal ions are thermally unstable chelate complexes. These complexes are such that they release metal ions at the desizing operating temperature (say 100 F. or over) but at lower temperature hold the ions as non-catalytic complexes. With such materials it is possible to prepare a large supply of metal-containing peroxide solution and store it at room temperature without catalyzed peroxide decomposition. Examples of chelating agents which can form such complexes are the amino carboxylic acids, especially amino carboxylic acids having not more than 2 carbon atoms separating the carboxyl group from the amino nitrogen atom, such as the pyridine- Z-carboxylic acids. An especially preferred subgroup of these chelating agents are those having a pyridine ring which is substituted by a single carboxy group attached to the 2-position of the ring, as for example, picolinic acid, 4-methyl-picolinic acid, and the like.

and the like; copper can be.

The hydrogen peroxide concentration in the aqueous desizing solution is advantageously maintained between about 0.01% and about 0.4% by weight, with concentrations between about 0.02 and about 0.2% by weight being preferred. Higher concentrations of hydrogen peroxide may be employed if desired. As a general rule, however, less peroxide is required when catalysts are present than when they are not employed.

Surface active agents (wetting agents) both ionic and nonionic may optionally be added to desizing solutions according to the invention. Suitable wetting agents comprise long chain alcohol ethoxylates, fatty acid soaps, petroleum sulfonates, alkali metal petroleum sulfonates, sulfated alcohols, alkyl-benzene sulfonates and the like. Preferred wetting agents comprise nonionic wetting agents especially long chain alcohol ethoxylates, e.g., C -C alkyl polyoxyethyl alcohols of 3-20 oxyethyl groups. These long chain alcohol ethoxylates improve desizing performance by increasing fabric wetting. Wetting agents especially pre- 'ferred comprise blends of polyoxyethylated C -C linear alkyl alcohols of from 3 to oxyethyl groups.

Surface active agent concentration in the desizing solution is advantageously maintained between about 0.05 to about 0.25% by weight with concentrations of from 0.075 to about 0.15% being preferred.

Conventional starch-desizing enzymes (amylases) are on occasion incorporated into solutions according to the invention to provide a desizing solution effective for the removal of polyvinyl alcohol starch combination sizings. Enzymes such as, for example, Wallerstein Co.s Rapidase, Premier Malt Products, Inc.'s Exsize HA and Amizyme Tablets, Metro-Atlantic Inc.s Atcozyme, Woonsocket Color and Chemical Co.s Wooncozyme L and Jersey State Chemical Co.s J-Zyme 30 may be suitably employed. These conventional enzymes are quite effective at the pH's of the instant desizing solutions. When enzyme is employed, concentrations of up to about 4% by weight are suitable with concentrations of from about 0.2% to about 2% by weight being preferred.

The catalyst addition in accordance with this invention is useful with all hydrogen peroxide desizing processes. This includes both the highly alkaline conventional processes and the process of US. 3,682,583 employing a pH of 4 to 9. Because of the many advantages inherent in the use of a pH 49. as described in U.S. 3,682,583, it is preferred to use the present catalyst addition with aqueous hydrogen peroxide solutions having pHs in the range of from pH 4 to pH 9, most preferably, pH 6 to pH 8.

At times in order to maintain the pH within the preferred range it may be desirable to incorporate into the desizing solution a minor amount of a pH-buffering material such as an alkali metal salt of a weak or intermediate acid, for example. alkali metal bicarbonates and dihydrogen phosphates. Preferred buffering materials comprise alkali metal dihydrogen phosphates. Generally, additions of buffering material of not more than about 0.03% by weight are useful with amounts of from about 0.001 to 0.02% by weight being preferred. Higher concentrations of buffering material may be used, if needed to maintain the desired pH.

Alkali metal silicates are a common component of conventional fabric treating solutions, especially bleaching solutions, where they impart added whiteness to the fabric. While such silicates may be added to the present solutions it is preferred to not do so as they tend to slow the desizing rate.

Operating Conditions Fabric treatment with the solution according to the invention is suitably carried out at between about 80 F. and 212 F. preferably from 120 to 212 F. with tem peratures of from 150 F. to 212 F. being most preferred. With temperatures in the general range one can ordinarily obtain suitable desizing with desizing times of from about 0.25 to about 30 minutes. With the preferred temperatures generally from about 0.5 to about 15 minutes are required for good desizing of most fabrics. Some heavyweight fabrics may require longer times to effect complete penetration by the desizing solutions.

Any of the conventional continuous or batch methods of applying desizing solution to fabrics can be employed in carrying out the desizing with the new desizing compositions. A simple and effective procedure is to contact, e.g. by immersion, the fabric with the desizing solution at the operating temperature until the desired desizing action has taken place. In a continuous process the fabric can be pulled at a regulated rate through a bath of heated desizing solution. In another continuous process the fabric can, for instance, be first padded in open width with the new desizing solution, either warm or cold. Then, atfer leaving the padding mangle, the goods can be passed to a steamer or passed through a pot-eye to convert them into rope form followed by heating and piling into a J-Box where the desizing is completed by heating. Because of the low temperatures used with the instant catalyzed desizing process, it is generally possible to desize polyvinyl alcohol in the same apparatus used for removing conventional starch size. The desizing is followed by the usual washing treat ments. Still other procedures are applicable, the invention not being limited with respect to the methods by which the new desizing solutions are applied to the fabric which is to be desized.

The Fabric Treated The desizing process of this invention is effective with all types of fabrics, including difiicult to desize heat set fabrics. Heat setting is a brief exposure to high temperatures, e.g., 10 seconds at 400 F., applied to improve the dimensional stability and easy-care properties of synthetic fabrics. Thi". heat treatment is conveniently carried out prior to desizing. Polyvinyl alcohol exposed to this treatment is extremely difficult to remove by conventional means. The process of this invention may be used to remove all types of polyvinyl alcohol including fully hydrolyzed and partially hydrolyzed grades.

The following examples demonstrate the polyvinyl alcohol desizing effectiveness of hydrogen peroxide solutions containing catalysts in accordance with this invention. They are not to be construed as limiting the inven tion.

EXAMPLE I AND COMPARATIVE EXPERIMENT A The effectiveness of hydrogen peroxide solutions as polyvinyl alcohol desizing agents is to a major extent related to the ability of hydrogen peroxide to oxidatively cleave polyvinyl alcohol molecules and produce lower molecular weight polyvinyl alcohol fragments. These lower molecular weight fragments are not only more water soluble than the parent molecules, but, importantly, produce relatively lower viscosity solutions having a much reduced tendency to form gels and re-deposit on the fabric or equipment. The relative polyvinyl alcohol cleavage effectiveness of hydrogen peroxide-containing desizing agents can be determined by measuring the rate of decrease of viscosity of polyvinyl alcohol solutions following treatment with a desizing agent. Effective hydrogen peroxide desizing agents cleave the polyvinyl alcohol molecules in the solution to a substantial degree and rapidly decrease the viscosity.

A 6% by weight solution of high molecular weight fully hydrolyzed polyvinyl alcohol (Air Reduction Companys Vinol 350) was prepared. Ferric ion, as 0.1% by weight of Fe(NO -9H O, was added to a sample of this solution. The sample was heated to F., a temperature too low for effective desizing by conventional processes. One percent by weight of hydrogen peroxide was added and the viscosity in centipoise units was repeatedly measured. For purposes of comparison the experiment was repeated, this time omitting the metal ion catalyst. The viscosities observed in both experiments are given in Table I.

TABLE I Solution viscosity, cps.

With ferric ion Without ferric ion Tings, minutes:

EXAMPLE II AND COMPARATIVE EXPERIMENT B EXAMPLE III AND COMPARATIVE EXPERIMENT C Ferric ion is a very effective metal ion catalyst. It does, however, have a red-brown color which may be undesirable in certain applications. Cobalt ion gives excellent results and has a very faint pink color. The effectiveness of cobalt ion was demonstrated using the general method of Example I.

A 6% by weight solution of polyvinyl alcohol containing 1% by weight hydrogen peroxide was prepared. A sample was heated to 150 F. and treated with 0.07% w. of Co(NO,),-6H;O. Viscosity was measured initially and after minutes. For comparison a sample was heated without any hydrogen peroxide and a second sample was heated without any catalyst. The initial viscosities were all about 200 cps. The cobalt ion catalyzed sample had a viscosity, after 10 minutes, of 80 cps. The non-catalyzed sample had a viscosity of 188 cps. while the peroxide-free sample had a viscosity of 206 cps. after 10 minutes.

EXAMPLE IV The experiment of Example III was repeated using varying amounts of cobalt ion catalyst and 0.5% by weight of hydrogen peroxide. When 0.01% by weight of Co(NO -6H O was used as catalyst a 10 minute heating at 150 C. reduced viscosity to 143 cps. With 0.05% by weight of Co(NO -6H O, the viscosity was cps. With 0.10% by weight of Co(NO -6H O, the viscosity was about 10 cps.

EXAMPLE V AND COMPARATIVE EXPERIMENT D A 6% by weight polyvinyl solution of fully hydrolyzed high molecular weight alcohol containing 0.5% by weight hydrogen peroxide was prepared. A sample was heated to 150 F. and treated with 0.1% w. of the several transition metal catalyst materials listed in Table II. Viscosity was measured initially and after 10 minutes. For comparison a sample was heated without any hydrogen peroxide and a second sample Was heated without any catalyst. The initial viscosities were all about 220 cps. The viscosities after heating are given in Table II.

6 TABLE II Catalyst: Viscosity, cps. No catalyst 210 No HP-no catalyst 218 .FG(NO3)3'9HQO CU(NO3)Q'3HQO 4 Co(N0 ),-6H;O 27 MnSO -H,O 160 ZnSO,-6H O 201 CdSO, 195 TiSO, 204

EXAMPLE VI AND COMPARATIVE EXPERIMENT E v To illustrate that very low concentrations of copper ion may be employed, a 6% by weight solution of fully hydrolyzed high molecular weight polyvinyl alcohol con taining 0.2% by weight hydrogen peroxide was prepared. A sample was heated to 200 F. with about 1.5 parts per million by weight of copper ions in the form of CuCIQ'ZHQO For comparison, a sample was heated without any hydrogen peroxide and a second sample was heated without any catalyst. The initial viscosities were all about 220 cps. The viscosities after heating are given in Table III.

TABLE III Catalyst: Viscosity No catalyst 211 No hydrogen peroxide, no catalyst 220 1.5 ppm. copper ions 15 I claim as my invention:

1. In a process for removing polyvinyl alcohol-containing size from fabric wherein the fabric is contacted with an aqueous solution of hydrogen peroxide and thereafter washed, the improvement which comprises contacting in the presence of a catalytically effective amount of'ions of a transition metal selected from copper, iron and cobalt at a temperature from about F. to about 212 F. for a period from about 0.25 to about 30 minutes.

2. The process in accordance with claim 1 wherein the ions of a transition metal are cobalt or iron.

3. The process in accordance with claim 1 wherein the ions of a transition metal are copper ions.

4. A process for removing polyvinyl alcohol-containing size from fabric which comprises applying to the fabric an aqueous solution having a pH in the range of 4 to 9 and consisting essentially of water, from about 0.02% to about 0.4% by weight of hydrogen peroxide and an amount of ions of a transition metal selected from the group consisting of (1) about p.p.m. to 5,000 ppm. by weight of ions of iron and cobalt, and (2) from about 1 to about 1,000 p.p.m. of copper; maintaining the fabric, wetted by the aqueous solution, at temperatures in the range of F. to about 212 F. for from about 0.25 minutes to 30 minutes; and then washing the fabric.

5. The process in accordance with claim 4 wherein the temperature is in the range of from to 212 F. and the time is from 0.5 to 15 minutes.

References Cited UNITED STATES PATENTS 2,803,517 8/1957 White 8--138 3,595,603 7/1971 Cerana 8-111 3,682,583 8/1972 Kravetz et al 8-438 3,398,096 8/1968 Das et al 252-95 BENJAMIN R. PADGETT, Primary Examiner US. Cl. X.R. 

